Technical Field
The present disclosure relates to laths, which may for example be used as a building material in stucco systems.
Description of the Related Art
One coat stucco systems were developed in the 1970's as a means to improve building wall energy efficiencies without increasing construction cost. Such stucco systems are applied over one inch thick expanded polystyrene (“EPS”) insulating foam board. The EPS foam board increases thermal resistance and hence improves energy efficiency. Traditional stucco is ¾ inch to ⅞ inch thick and requires a two coat application process. In contrast, one coat stucco is approximately ⅜ inch to ½ inch thick and can be applied in only one coat. Thus one coat stucco systems reduce costs with respect to traditional stucco systems due to savings in material as well as installation labor.
Traditionally, one coat stucco systems used one inch woven wire hexagonal laths. Such lath is specified in ASTM C1032 “Standard Specification for Woven Wire Plaster Base”. For one coat stucco, the lath is prescribed as having one inch hexagonal openings, and a wire size of 0.034 inch diameter, with the lath having a weight of 0.88 pounds per square yard. Such lath is produced in rolls of 36 inch width and 150 feet in length. A roll would contain 50 square yards and should weigh 44 lbs.
As noted, woven wire lath can be packaged in rolls, which improves installation efficiency since the lath lays flat when unrolled, and tufts well at attachment points when affixed to a suitable substrate such as EPS foam board using appropriate fasteners. These features provide the ability to achieve thin plaster coats with little or no telegraphing of the lath on the finished stucco surface. However, competitive pressures, have resulted in decreases in the wire size and increases in the opening sizes in woven wire lath. As a result of these changes, roll weights have decreased from about 45 pounds to about 35 pounds—a 22% decrease. This lighter lath results in stucco finishes that no longer perform at the prescribed or expected levels.
Further, the design of the woven wire hexagonal lath is such that the wire strands forming the hexagons do not lie in a straight line. Instead, the wires form a staircase shape that is less effective in providing reinforcement to the cured stucco finish, resulting in increased stucco cracking. Further, woven wire lath requires two parallel wire segments be twisted together to form at least two sides of the hexagon. This is an inefficient use of material since additional wire is necessary to form the twists, but serves no functional purpose in the stucco application.